Galvanometer



R. G. PIETY GALVANOMETER Oct. 6, A1959 2 Sheets--Sheet lV Filed Nov. 21, 1955 INVENTOR. R. G. PIETY BYM w ATTORNEYS R. G. PIETY GALVANOMETER Oct. 6, 1959 2 Sheets-Sheet 2 Filed Nov. 2l. 1955 INVENTOR.

R.G. PIETY y BYAM YW.

' ATTORNEYS l United States Patent GALvANoMETER YRaymond G. Piety, Bartlesville, Okla., assiguor to Phillips Petroleum Company, a corporation of Delaware Application November 21, 1955, Serial No. 547,963

2 Claims. (Cl. 324-150) This invention relates to galvanometer construction. In one aspect it relates to a galvanometer of very small sizefor use in instrument work. In another aspect it `relates to a galvanometer of the moving coil type.

An object of this invention is to provide a galvanometer of the moving coil type for use in instrument work.

Another object of this invention is to provide such a galvanometer which can be constructed of a very small s1ze.

Yet another object of this invention is to provide such a galvanometer which is very sensitive and adapted to indicate the ilow of electric currents of small magnitude.

Still another object of this invention is to provide a galvanometer having compactness, ruggedness and a large mirror surface suitable for use in recorders, such as seismic recorders.

. Still other objects and advantages will be realized upon reading the following description which taken with' the attached drawing forms a part of the disclosure.

In such recorders, as seismic recorders, it is necessary to mount a number of galvanometers compact-ly so as to operate upon one chart strip. The mirrors are relatively large so as to make eticient use of light in high speed photographic recordings.

I accomplish these and other objects and advantages by providing a galvanometer coil comprising windings of an insulated metal ribbon, the portions of said coil comprising the edges ofV said metal ribbon being termed the sides of said coil, said coil having such a shape that avtransverse section through a midpoint longitudinally of said coil exhibits one convex side and one concave side, and said coil being adapted to rotate on a radius perpendicular to the longitudinal axis thereof.

I further provide a galvanometer comprising, in combination, a U-magnet and a movable coil wound of insulated metal ribbon and disposed adjacent the pole ends of said magnet, the ends of said U-magnet being right cylindrical surfaces convex with respect to the body of the magnet, said surfaces facing one another and having mutuallyparallel longitudinal axes, the portions of said coil comprising the edges of said metal ribbon being termed the sides of said coil, said coil having substantially a concavo-convex cross section with the convex side facing the ends of said magnet and conforming substantially thereto, the longitudinal axis of said coil being parallel to said longitudinal axis of the surfaces of the pole ends of said U-magnet and said coil being adapted to rotate on a radius perpendicular to its longitudinal axis.

My galvanometer is made with either one or two U- type permanent magnets with beveled ends to form surfaces corresponding close to the sides of a movable coil disposed adjacent the ends of one magnet when one magnet only is employed and intermediate the ends of two magnets in case of two magnets. When one magnet only is used, I prefer to employ a magnetic material, such as soft iron, to concentrate the lines of force on the side of the coil opposite the magnet.

P YICC lto the magnet poles for ease of movement of the coil.

The coil is mounted on a ilexure plate so as to rotate 'around the line of liexure of the fiexure plates. In one form a magnetic material such as soft iron is positioned on the side of the coil opposite one permanent magnet and in a second embodiment a second permanent mag- 'net ispositioned on the side of the coil opposite the iirst permanent magnet. The magnetic material or the second permanent magnet have their ends shaped in a convex or concave form to fit substantially the back side of the coil. In this manner very sensitive galvanometers are produced ,either with use of a 'single magnet or with use of two magnets. A reilecting mirror is mounted so as to rotate with the coil for indication of the flow of current. These structures are mounted preferably on an aluminum base to form a Very rigid and strong apparatus, even though very small.

The term right cylindrical surface as set forth in this specification and claims is intended to include confgura tions having the cross section of an elliptical arc as well as of a circular arc.

I'he beveled end surfaces of the U-magnets and of the magnetic material as contemplated herein are under some conditions merely plane surfaces so disposed asto approximate the arc of a circle alongvwhich lthe concave and/or convex surfaces of the coil move in close proximity thereto in the normal galvanorneter operation.

. In the drawing,

Figure l is a perspective view, with parts cut away, illustrating one embodiment of my invention.

Figure 2 is a cross sectional view, in part, of a portion of theapparatus of Figure 1 on an enlarged scale.

A Figure 3 is a perspective view, with parts cut away, of. the second embodiment of my invention. Q Figure 4 is a perspective view of a portion o-f the apparatus of Figure 3.

Figure 5 is a cross sectional View of a part of the apparatusr of Figure 3.

' Figure 6 is a plan View, in section, illustrating the apparatus of Figure 1.

, f Referring now to the drawing `and specifically to FigaA coil, lpprefer to use anodized aluminum` ribbon4 so that` ure l, reference numeral 11 identities a base or body member which is preferably made of aluminum. At,

tached by screws 17 to one end of body member 11 is a column 13 of magnetic material. A column 15 is attached to the opposite side of the base member 11 by a pair of screws similar to screws17 and not shown. A permanent U-magnet 19 is positioned on a raised portion of base 11 as shown. The poles of the U-magnet are ground out or beveled and these ground vout surfaces are identified by reference numeral 20. Disposed adjacent these surfaces is a coil 27 constructed of many turns of an aluminum ribbon; The particular construction of this coil is best seen when referring to Figure v2 which illustratesin cross section this construction. The coil is wrapped upon a base of an insulating material such asv sta-ntially flush with the side surfaces of the base and` for the second winding the aluminum ribbon is offset a slight distance to one side and then the entireturn made in that offset manner. For the next turn the ribbon isoffset still further to the same side and'so on until as many, turns as desired are made. For making such,

each successive ttun of the coil will be insulated from the previous turn. Whena suflicient number of turns have been made the resulting coil should have a cross section such as that illustrated in Figures 2 and 5, that is,

Aone of the sides of the coil has substantially a convex surface and the other side substantially a concave surface so that the concave surface 26 of Figure 2. can be positioned adjacent the beveled ends of the U-magnet V19 and the coil rotated on a radius at least a short distance -without touching the magnet.

in the shape of a triangle with the base side of the triangle being positioned adjacent the coil support 37. The triangle base is glued or otherwise attached to the coil support 37. This coil support member 29 can be clearly observed in Figure l and as mentioned as identified by reference numeral 29. The upper open end of side triangle being shown in relation to the coil support 37. The opposite end of this coil support member 29 is so formed as to result in the production of a pair of ilexure plate springs 31 shown at the top of the support member 29 and at the bottom thereof between the lower portions of the columns 13 and 15. These exure plate springs 31 when positioned in the structure as illustrated in Figure l hold the coil in a proper position with respect to the convex surfaces 18 of the columns of magnetic material 13 and 15 and the ends 20 of the U-magnet.

The portion of the coil support assembly 29` intermediate the ilexure plate springs 31 is formed into the form of another triangle with a mirror 33 attached to the base side thereof.

Electrical conducting wires or preferably extensions of the ends of the coil ribbon are attached to the two ends of the aluminum ribbon of the coil and these wires are passed through openings in the base member 11, or preferably extensions of the ends of the coil ribbon extend through openings 25. On the back side of the base member 11 the wires or ribbon ends protrude and extend on through corresponding openings in an insulating material 43 to the back side of the apparatus to binding posts, not shown. A pair of wires 45 extend from binding posts for `attachment of service wires as desired. Block 21 is held tightly against the top` of the U-magnet 19 by a screw 23 threaded into base member 11. A screw 35 extends through the upper portion of the column 15 and part way into the upper and cut-away portion of column 13 for rigidly holding the upper exure plate spring 31 in position. A small opening 39 in the upper exure spring 31 is for accommodation of screw 35. The ends of the mirror support assembly which formed the above mentioned triangles are soldered at 41 to make the assembly rigid.

In the operation of this embodiment of my galvanometer upon attaching wires 45 to a source of electric current the coil 27 moves to the left or to the right as the flexure plate springs 31 ilex. In all galvanometers the greater the current which is owing through the coil the greater the degree of exing and upon previous calibration of the instrument the current in terms of amperes can be read directly.

In order to read this instrument a source of light is provided for directing a beam of light against mirror 33 and a scale is positioned at some convenient distance from this mirror for measuring the degree of rotation of the coil. By previous calibration of this instrument the current flowing through the coil is determined within the range of the instrument.

In Figure l, the U-magnet 19 and coil 27, and thev coil 27 and the magnetic members 13 and 15 are illustrated as being separated from each other by greater distances than used in construction of the apparatus so that these parts can be visualized more clearly. The

sectional view of Figure 6 illustrates positioning of these members employed in construction of the apparatus.

The term aluminum ribbon or metal ribbon as used throughout this specification and claims is intended to include wire of other cross section than rectangular. This winding material is -a wire of circular, oval or elliptical, or of rectangular cross section, the latter being preferred. While l have described the coil of my in- Vention as being wound from an aluminum ribbon, copper or other electrical conducting material suitable for the purpose can be used when suitably insulated.

Figure 2 shows on an enlarged scale the true construction of the coil, with the offset windings of ribbon.

in Figure 3 of the drawing is a second embodiment of my invention in which l employ a pair of permanent magnets in place of just one magnet and a `soft iron magnetic material. In this second embodiment the apparatus comprises a base or body member 51 preferably made of aluminum in the general form as illustrated in Figure l. A vertically disposed column 53 is provided as shown and around this column is disposed a permanent U-magnet 61 having its ends 6u beveled or made in a concave form similar to the ends 26 of magnet 19 of Figure l. A clamp 87 preferably of aluminum holds lthe U-magnet 61 rigidly in place upon insertion and tightening of a screw 81. Near the opposite end of base 51 is the second permanent U-magnet 63. This magnet is held rigidly in place by a screw 79 extending through a holder plate 59 and threaded into a split column assembly SS. The ends of permanent magnet 63 are beveled or made in the form of convex surfaces 61. The convex surfaces 61 correspond to the concave surfaces 60 of magnet 61. Disposed between the convex and concave surfaces of the two magnets is a coil 65 constructed in the same manner as the coil of Figure l. This coil 65 has a convex side 64 facing the concave side 60 of U-magnet 61 and a concave side 66 facing the convex ends of Umagnet 63.

The split column assembly 55 is composed of several parts. One part, the main column 54 is rigidly attached such as by a screw, not shown, to the base 51 and an insert 56 is attached to the main column 54 by`screws 58. The purpose of this insert 56 is to hold the flexure plate spring 67 of the spring coil support 69 between the column 54 and the insert. This spring coil support 69 is clearly illustrated in perspective in Figures 4 and 5. On one end of the plane section 67 is formed a triangle 71 to the base of which is attached by glue or other suitable means a coil form 73 similar to coil support 37 of Figure l. One side of the `triangle is soldered at 68 to make the assembly rigid. A mirror 75 is attached, for example, by shellac or other suitable adhesive to a mirror support 79, the legs of which straddle the flexure spring plate 67 adjacent the triangle 71 and these legs areY then glued or shellacked for hrm attachment thereto. Wires 83, or preferably extended ends of the coil ribbon, extend from the coil through holes in the base member 51 to binding posts, not shown, on the bottom side of an insulator block 57.

In one example there has been made a coil such as coil 65 and coil 27 by wrapping an aluminum ribbon, about .001 iwnc-rthick by .018 inch wide, anodized for insulation around a base for about 25 turns. The flexure plate sprmg member of both Figures l and 3 are preferably made of beryllium copper alloy sheet material about .004 inch thick. The coil form 37 of Figure l and form 73 of Figure 3 are made of a linen base synthane material which I find is Very satisfactory for the purpose. Adhesive sticks easily to this material for firm attachment to the coil support portion of the coil supports 29 and 71.

The galvanometer of Figure 3 is prepared for use by calibration in the same general manner as mentioned relative to the apparatus of Figurel, that is, by basing a known-current through the coil and determining the degree of rotation of the coil as indicated by a reflecting beam of light from the mirror and then passing a current of unknown amperage through the coil.

In one case a galvanometer made according to Figure l is one inch long by one-half inch wide by 15/16 of an inch high. A galvanometer made accord-ing to Figure 3 was one and three-eighths inches long, by one-half inch Wide by one and one-half inches in overall height. Of this height one-half inch was required by the mirror which was positioned abo've the galvanometer apparatus proper.

The beveled surfaces of the ends of the magnetic matenial and of the U-magnets can, if desired, be surfaces cylindrical in shape or if desired they can be plane surfaces. The magnets, or the magnet and magnetic material are so positioned that upon rotation of the coil the edges of the coil will not touch any of the adjacent surfaces. It is preferable to construct these surfaces substantially cylindrical in form so that the coils can be rotated any reasonable degree without contacting metal and yet be in very close proximity thereto.

Figure 6 illustrates a sectional view taken on a plane parallel to the base of the galvanometer and about midway up from the base. This figure is intended to illustrate the small clearance between the beveled edges 20 and coil 27, and between the coil and the convex curved surfaces 18 of the columns 13 and 15. The reference numerals illustrated in Figure 6 refer to like parts of Figure 1 with the exception that bind posts or connectors 45A are visible only in Figure 6.

The galvanometer of my invention is, when desired, a very small instrument. In one case it measured less than two inches in length and less than one inch in width and of corresponding height. In spite of its. small dimensions it is very rugged and of strong construction. In recording units for seismic recordings, etc., it is necessary to mount a number of galvanometers compactly so as to operate upon a singler chart. The mirrors are relatively large so as to make eicient use of light in high speed photographic recordings.

While certain embodiments of the invention have been described for illustrative purposes, the invention obviously is not limited thereto.

I claim:

1. A galvanometer comprising, in combination, a U- shaped magnet horizontally disposed, a magnetic member near the pole ends of said magnet and a coil movable therebetween, the pole ends being right surface sections of a common right cylinder, said sections having their vertical axes mutually parallel, the vertical lengths of said surface sections being longer than their widths and said` surface sections being concave inward toward the body yof the magnet and facing each other, said coil being wound of an insulated metal ribbon upon a base of insulating material, one edge of each successive turn of said metal ribbon extending beyond the corresponding edge of the next preceding turn on one side of said coi1 in such a manner that a horizontal section of said coil exhibits one convex side and one concave side, the vel'- tical length of said coil being greater than its width, said magnetic member having two end surfaces corresponding to the end surfaces of said magnet, the end surfaces of said magnetic member being right cylindrical surface sections of a common right cylinder, these latter right surface sections having their vertical axes mutually parallel and parallel to the vertical axes of the surfaces of the pole ends, the vertical lengths of said latter right surface sections being longer than their widths, said latter sections' being convex outward from the body of said magnetic member and opposed to each other, the convex outward surfaces of the magnetic member end surfaces conforming to the adjacent side of said coil, and the other side of said coil conforming to the end surfaces of said magnet, a vertically disposed flexure plate, one end of said plate being supported by said magnetic member, the base of said coil being attached to said ilexure plate at a position opposite said end of said plate in such a manner that as an electric current passes through said coil the coil rotates around its vertical axis thereby flexing said flexure plate in proportion to the current flowing through said coil.

2. In the galvanometer of claim 1, a mirror rigidly supported by said flexure plate for reilecting a beam of light.

References Cited in the le of this patent UNITED STATES PATENTS 866,387 Richard Sept. 17, 1907 1,187,377 Onwood June 13, 1916 1,527,162 Alvord Feb. 24, 1925 1,595,838 Turner Aug. 10, 1926 2,013,764 Putnam Sept. 10, 1935 2,729,789 Ransier Ian. l3, 1956 

